Difference between mass and weight

We generally tend to confuse the terms mass and weight, although these physical properties are completely different. However, given this common and also frequent error, it is worth highlighting and clarifying the difference between mass and weight.

Physical definitions

Mass

It is a scalar quantity that measures the amount of matter in a body. It is invariable, regardless of where the body is, the mass will always be the same. The International System of Units (SI) the one represented in kilogram (kg) also usually uses the pounds (Lb).

Weight

It is a vector quantity, it represents direction, intensity and sense. As such, it is defined as the measure that results from the action exerted by earth's gravity on the body, it is a variable measure, it varies according to the place where said body is located. The International System of Units (SI) represents it in Newton (N).

The weight can be calculated using the following formula:

P = m * g where "m" is the mass and "g" is the acceleration of gravity. It is worth remembering that the value of gravity on earth is approximately 10 m / s2.

Differences between mass and weight

According to these definitions the key differences between mass and weight They are:

Mass (m)	Weight (p)
It is a scalar quantity.	It is a vector magnitude.
It's the amount of matter a body has.	It is the action exerted by the force of gravity.
Its value is constant.	Its value varies by position.
It is measured with the balance.	It is measured with the dynamometer.
Unit of measurement: kilogram (Kg) and gram (g).	Unit of measurement: Newton (N).

These are two terms that are often used interchangeably in everyday life, the People refer to the mass of a body as its weight and speak of weight to refer to mass. In other words, the term "mass" is used daily as "weight", when the latter is related to matter and not to mass.

What led to the separation of these two properties of matter was Newton's development of the concept of weight from the Laws of Motion and the Law of Universal Gravitation.

Curiosities

Did you know that by measuring our weight, we actually measure our mass?

When we stand on a scale to weigh ourselves, we usually call that our weight, we are actually measuring it is our mass, that is, the amount of matter in our body. There are other machines that can really measure our weight, these are not as used and they work standing for a moment on them and at the end gives a true weight value also expressed in Newtons.

Does the weight vary depending on where we are?

We do not weigh the same on the moon and even in space, where there is no gravity, the mass remains constant but the weight is zero.

The mass is based on the volume that a body occupies, the weight shows the energy of that object with respect to the attraction that gravity exerts with another object. On earth, weight is determined by the force with which the earth draws us to the ground. Being exact, we do not weigh the same at the top of a mountain as at sea level, so standards have been established worldwide to avoid misunderstandings, since the difference is very small.

On the other hand, it is worth noting that our body in the water weighs less due to the buoyancy exerted by a force contrary to the force of gravity.

Types of mass and weight

From a scientific point of view, understanding that the mass and weight are quantities with which the matter contained in a body and the force exerted by gravity on it are measured respectively, the types of these best known and used are:

• Atomic mass: The mass of an atom.
• Molar mass: The mass of one mole of a substance.
• Molecular mass: The mass of a molecule of a substance.
• Inertial mass: That physical magnitude that indicates the resistance of a body to a change in speed.
• Body mass: It is the mass of a person's body.
• Atomic weight: It is the average mass of the atoms of an element.
• Molecular weight: It is the result of the sum of the atomic weights of the elements that form a compound.